Mention need for possible PSID reset for some OPAL drives in man page.

Fixes: #879

man/common_options.adoc

@@ -337,6 +337,7 @@ ifdef::ACTION_ERASE[]
 Erase *ALL* data on the OPAL self-encrypted device, regardless of the partition it is ran on, if any,
 and does not require a valid LUKS2 header to be present on the device to run. After providing
 correct PSID via interactive prompt or via *--key-file* parameter the device is erased.
+PSID is usually printed on the OPAL device label (either directly or as a QR code).
 endif::[]
 
 ifdef::ACTION_LUKSFORMAT[]

man/cryptsetup-luksFormat.8.adoc

@@ -29,8 +29,12 @@ in use, e.g., mounted filesystem, used in LVM, active RAID member, etc. The
 device or filesystem has to be un-mounted in order to call luksFormat.
 
 To use specific version of LUKS format, use _--type luks1_ or _type luks2_.
+
 To use OPAL hardware encryption on a self-encrypting drive, use
-_--hw-opal_ or _--hw-opal-only_.
+_--hw-opal_ or _--hw-opal-only_. Note that some OPAL drives can require
+a PSID reset (with possible deletion of data) before using the LUKS format
+with OPAL options.
+See  _--hw-opal-factory-reset_ option in cryptsetup _erase_ command.
 
 *<options>* can be [--hash, --cipher, --verify-passphrase, --key-size,
 --key-slot, --key-file (takes precedence over optional second argument),